/*
 *  TLS server tickets callbacks implementation
 *
 *  Copyright The Mbed TLS Contributors
 *  SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
 *
 *  This file is provided under the Apache License 2.0, or the
 *  GNU General Public License v2.0 or later.
 *
 *  **********
 *  Apache License 2.0:
 *
 *  Licensed under the Apache License, Version 2.0 (the "License"); you may
 *  not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *  http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 *  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *
 *  **********
 *
 *  **********
 *  GNU General Public License v2.0 or later:
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License along
 *  with this program; if not, write to the Free Software Foundation, Inc.,
 *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 *  **********
 */

#if !defined(MBEDTLS_CONFIG_FILE)
#include "nettls/config.h"
#else
#include MBEDTLS_CONFIG_FILE
#endif

#if defined(MBEDTLS_SSL_TICKET_C)

#if defined(MBEDTLS_PLATFORM_C)
#include "nettls/platform.h"
#else
#include <stdlib.h>
#define mbedtls_calloc calloc
#define mbedtls_free   free
#endif

#include "nettls/ssl_internal.h"
#include "nettls/ssl_ticket.h"
#include "nettls/platform_util.h"

#include <string.h>

/*
 * Initialze context
 */
void mbedtls_ssl_ticket_init(mbedtls_ssl_ticket_context* ctx)
{
    memset(ctx, 0, sizeof(mbedtls_ssl_ticket_context));

#if defined(MBEDTLS_THREADING_C)
    mbedtls_mutex_init(&ctx->mutex);
#endif
}

#define MAX_KEY_BYTES 32 /* 256 bits */

#define TICKET_KEY_NAME_BYTES  4
#define TICKET_IV_BYTES        12
#define TICKET_CRYPT_LEN_BYTES 2
#define TICKET_AUTH_TAG_BYTES  16

#define TICKET_MIN_LEN      (TICKET_KEY_NAME_BYTES + TICKET_IV_BYTES + TICKET_CRYPT_LEN_BYTES + TICKET_AUTH_TAG_BYTES)
#define TICKET_ADD_DATA_LEN (TICKET_KEY_NAME_BYTES + TICKET_IV_BYTES + TICKET_CRYPT_LEN_BYTES)

/*
 * Generate/update a key
 */
static int ssl_ticket_gen_key(mbedtls_ssl_ticket_context* ctx, unsigned char index)
{
    int ret;
    unsigned char buf[MAX_KEY_BYTES];
    mbedtls_ssl_ticket_key* key = ctx->keys + index;

#if defined(MBEDTLS_HAVE_TIME)
    key->generation_time = (uint32_t)mbedtls_time(NULL);
#endif

    if ((ret = ctx->f_rng(ctx->p_rng, key->name, sizeof(key->name))) != 0)
        return (ret);

    if ((ret = ctx->f_rng(ctx->p_rng, buf, sizeof(buf))) != 0)
        return (ret);

    /* With GCM and CCM, same context can encrypt & decrypt */
    ret = mbedtls_cipher_setkey(&key->ctx, buf, mbedtls_cipher_get_key_bitlen(&key->ctx), MBEDTLS_ENCRYPT);

    mbedtls_platform_zeroize(buf, sizeof(buf));

    return (ret);
}

/*
 * Rotate/generate keys if necessary
 */
static int ssl_ticket_update_keys(mbedtls_ssl_ticket_context* ctx)
{
#if !defined(MBEDTLS_HAVE_TIME)
    ((void)ctx);
#else
    if (ctx->ticket_lifetime != 0) {
        uint32_t current_time = (uint32_t)mbedtls_time(NULL);
        uint32_t key_time = ctx->keys[ctx->active].generation_time;

        if (current_time >= key_time && current_time - key_time < ctx->ticket_lifetime) {
            return (0);
        }

        ctx->active = 1 - ctx->active;

        return (ssl_ticket_gen_key(ctx, ctx->active));
    } else
#endif /* MBEDTLS_HAVE_TIME */
    return (0);
}

/*
 * Setup context for actual use
 */
int mbedtls_ssl_ticket_setup(
    mbedtls_ssl_ticket_context* ctx, int (*f_rng)(void*, unsigned char*, size_t), void* p_rng, mbedtls_cipher_type_t cipher, uint32_t lifetime)
{
    int ret;
    const mbedtls_cipher_info_t* cipher_info;

    ctx->f_rng = f_rng;
    ctx->p_rng = p_rng;

    ctx->ticket_lifetime = lifetime;

    cipher_info = mbedtls_cipher_info_from_type(cipher);
    if (cipher_info == NULL)
        return (MBEDTLS_ERR_SSL_BAD_INPUT_DATA);

    if (cipher_info->mode != MBEDTLS_MODE_GCM && cipher_info->mode != MBEDTLS_MODE_CCM) {
        return (MBEDTLS_ERR_SSL_BAD_INPUT_DATA);
    }

    if (cipher_info->key_bitlen > 8 * MAX_KEY_BYTES)
        return (MBEDTLS_ERR_SSL_BAD_INPUT_DATA);

    if ((ret = mbedtls_cipher_setup(&ctx->keys[0].ctx, cipher_info)) != 0 || (ret = mbedtls_cipher_setup(&ctx->keys[1].ctx, cipher_info)) != 0) {
        return (ret);
    }

    if ((ret = ssl_ticket_gen_key(ctx, 0)) != 0 || (ret = ssl_ticket_gen_key(ctx, 1)) != 0) {
        return (ret);
    }

    return (0);
}

/*
 * Serialize a session in the following format:
 *  0   .   n-1     session structure, n = sizeof(mbedtls_ssl_session)
 *  n   .   n+2     peer_cert length = m (0 if no certificate)
 *  n+3 .   n+2+m   peer cert ASN.1
 */
static int ssl_save_session(const mbedtls_ssl_session* session, unsigned char* buf, size_t buf_len, size_t* olen)
{
    unsigned char* p = buf;
    size_t left = buf_len;
#if defined(MBEDTLS_X509_CRT_PARSE_C)
    size_t cert_len;
#endif /* MBEDTLS_X509_CRT_PARSE_C */

    if (left < sizeof(mbedtls_ssl_session))
        return (MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL);

    memcpy(p, session, sizeof(mbedtls_ssl_session));
    p += sizeof(mbedtls_ssl_session);
    left -= sizeof(mbedtls_ssl_session);

#if defined(MBEDTLS_X509_CRT_PARSE_C)
    if (session->peer_cert == NULL)
        cert_len = 0;
    else
        cert_len = session->peer_cert->raw.len;

    if (left < 3 + cert_len)
        return (MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL);

    *p++ = (unsigned char)((cert_len >> 16) & 0xFF);
    *p++ = (unsigned char)((cert_len >> 8) & 0xFF);
    *p++ = (unsigned char)((cert_len)&0xFF);

    if (session->peer_cert != NULL)
        memcpy(p, session->peer_cert->raw.p, cert_len);

    p += cert_len;
#endif /* MBEDTLS_X509_CRT_PARSE_C */

    *olen = p - buf;

    return (0);
}

/*
 * Unserialise session, see ssl_save_session()
 */
static int ssl_load_session(mbedtls_ssl_session* session, const unsigned char* buf, size_t len)
{
    const unsigned char* p = buf;
    const unsigned char* const end = buf + len;
#if defined(MBEDTLS_X509_CRT_PARSE_C)
    size_t cert_len;
#endif /* MBEDTLS_X509_CRT_PARSE_C */

    if (sizeof(mbedtls_ssl_session) > (size_t)(end - p))
        return (MBEDTLS_ERR_SSL_BAD_INPUT_DATA);

    memcpy(session, p, sizeof(mbedtls_ssl_session));
    p += sizeof(mbedtls_ssl_session);

#if defined(MBEDTLS_X509_CRT_PARSE_C)
    if (3 > (size_t)(end - p))
        return (MBEDTLS_ERR_SSL_BAD_INPUT_DATA);

    cert_len = (p[0] << 16) | (p[1] << 8) | p[2];
    p += 3;

    if (cert_len == 0) {
        session->peer_cert = NULL;
    } else {
        int ret;

        if (cert_len > (size_t)(end - p))
            return (MBEDTLS_ERR_SSL_BAD_INPUT_DATA);

        session->peer_cert = mbedtls_calloc(1, sizeof(mbedtls_x509_crt));

        if (session->peer_cert == NULL)
            return (MBEDTLS_ERR_SSL_ALLOC_FAILED);

        mbedtls_x509_crt_init(session->peer_cert);

        if ((ret = mbedtls_x509_crt_parse_der(session->peer_cert, p, cert_len)) != 0) {
            mbedtls_x509_crt_free(session->peer_cert);
            mbedtls_free(session->peer_cert);
            session->peer_cert = NULL;
            return (ret);
        }

        p += cert_len;
    }
#endif /* MBEDTLS_X509_CRT_PARSE_C */

    if (p != end)
        return (MBEDTLS_ERR_SSL_BAD_INPUT_DATA);

    return (0);
}

/*
 * Create session ticket, with the following structure:
 *
 *    struct {
 *        opaque key_name[4];
 *        opaque iv[12];
 *        opaque encrypted_state<0..2^16-1>;
 *        opaque tag[16];
 *    } ticket;
 *
 * The key_name, iv, and length of encrypted_state are the additional
 * authenticated data.
 */

int mbedtls_ssl_ticket_write(
    void* p_ticket, const mbedtls_ssl_session* session, unsigned char* start, const unsigned char* end, size_t* tlen, uint32_t* ticket_lifetime)
{
    int ret;
    mbedtls_ssl_ticket_context* ctx = p_ticket;
    mbedtls_ssl_ticket_key* key;
    unsigned char* key_name = start;
    unsigned char* iv = start + TICKET_KEY_NAME_BYTES;
    unsigned char* state_len_bytes = iv + TICKET_IV_BYTES;
    unsigned char* state = state_len_bytes + TICKET_CRYPT_LEN_BYTES;
    unsigned char* tag;
    size_t clear_len, ciph_len;

    *tlen = 0;

    if (ctx == NULL || ctx->f_rng == NULL)
        return (MBEDTLS_ERR_SSL_BAD_INPUT_DATA);

    /* We need at least 4 bytes for key_name, 12 for IV, 2 for len 16 for tag,
     * in addition to session itself, that will be checked when writing it. */
    MBEDTLS_SSL_CHK_BUF_PTR(start, end, TICKET_MIN_LEN);

#if defined(MBEDTLS_THREADING_C)
    if ((ret = mbedtls_mutex_lock(&ctx->mutex)) != 0)
        return (ret);
#endif

    if ((ret = ssl_ticket_update_keys(ctx)) != 0)
        goto cleanup;

    key = &ctx->keys[ctx->active];

    *ticket_lifetime = ctx->ticket_lifetime;

    memcpy(key_name, key->name, TICKET_KEY_NAME_BYTES);

    if ((ret = ctx->f_rng(ctx->p_rng, iv, TICKET_IV_BYTES)) != 0)
        goto cleanup;

    /* Dump session state */
    if ((ret = ssl_save_session(session, state, end - state, &clear_len)) != 0 || (unsigned long)clear_len > 65535) {
        goto cleanup;
    }
    state_len_bytes[0] = (clear_len >> 8) & 0xff;
    state_len_bytes[1] = (clear_len)&0xff;

    /* Encrypt and authenticate */
    tag = state + clear_len;
    if ((ret = mbedtls_cipher_auth_encrypt(
             &key->ctx, iv, TICKET_IV_BYTES,
             /* Additional data: key name, IV and length */
             key_name, TICKET_ADD_DATA_LEN, state, clear_len, state, &ciph_len, tag, TICKET_AUTH_TAG_BYTES))
        != 0) {
        goto cleanup;
    }
    if (ciph_len != clear_len) {
        ret = MBEDTLS_ERR_SSL_INTERNAL_ERROR;
        goto cleanup;
    }

    *tlen = TICKET_MIN_LEN + ciph_len;

cleanup:
#if defined(MBEDTLS_THREADING_C)
    if (mbedtls_mutex_unlock(&ctx->mutex) != 0)
        return (MBEDTLS_ERR_THREADING_MUTEX_ERROR);
#endif

    return (ret);
}

/*
 * Select key based on name
 */
static mbedtls_ssl_ticket_key* ssl_ticket_select_key(mbedtls_ssl_ticket_context* ctx, const unsigned char name[4])
{
    unsigned char i;

    for (i = 0; i < sizeof(ctx->keys) / sizeof(*ctx->keys); i++)
        if (memcmp(name, ctx->keys[i].name, 4) == 0)
            return (&ctx->keys[i]);

    return (NULL);
}

/*
 * Load session ticket (see mbedtls_ssl_ticket_write for structure)
 */
int mbedtls_ssl_ticket_parse(void* p_ticket, mbedtls_ssl_session* session, unsigned char* buf, size_t len)
{
    int ret;
    mbedtls_ssl_ticket_context* ctx = p_ticket;
    mbedtls_ssl_ticket_key* key;
    unsigned char* key_name = buf;
    unsigned char* iv = buf + TICKET_KEY_NAME_BYTES;
    unsigned char* enc_len_p = iv + TICKET_IV_BYTES;
    unsigned char* ticket = enc_len_p + TICKET_CRYPT_LEN_BYTES;
    unsigned char* tag;
    size_t enc_len, clear_len;

    if (ctx == NULL || ctx->f_rng == NULL)
        return (MBEDTLS_ERR_SSL_BAD_INPUT_DATA);

    if (len < TICKET_MIN_LEN)
        return (MBEDTLS_ERR_SSL_BAD_INPUT_DATA);

#if defined(MBEDTLS_THREADING_C)
    if ((ret = mbedtls_mutex_lock(&ctx->mutex)) != 0)
        return (ret);
#endif

    if ((ret = ssl_ticket_update_keys(ctx)) != 0)
        goto cleanup;

    enc_len = (enc_len_p[0] << 8) | enc_len_p[1];
    tag = ticket + enc_len;

    if (len != TICKET_MIN_LEN + enc_len) {
        ret = MBEDTLS_ERR_SSL_BAD_INPUT_DATA;
        goto cleanup;
    }

    /* Select key */
    if ((key = ssl_ticket_select_key(ctx, key_name)) == NULL) {
        /* We can't know for sure but this is a likely option unless we're
         * under attack - this is only informative anyway */
        ret = MBEDTLS_ERR_SSL_SESSION_TICKET_EXPIRED;
        goto cleanup;
    }

    /* Decrypt and authenticate */
    if ((ret = mbedtls_cipher_auth_decrypt(
             &key->ctx, iv, TICKET_IV_BYTES,
             /* Additional data: key name, IV and length */
             key_name, TICKET_ADD_DATA_LEN, ticket, enc_len, ticket, &clear_len, tag, TICKET_AUTH_TAG_BYTES))
        != 0) {
        if (ret == MBEDTLS_ERR_CIPHER_AUTH_FAILED)
            ret = MBEDTLS_ERR_SSL_INVALID_MAC;

        goto cleanup;
    }
    if (clear_len != enc_len) {
        ret = MBEDTLS_ERR_SSL_INTERNAL_ERROR;
        goto cleanup;
    }

    /* Actually load session */
    if ((ret = ssl_load_session(session, ticket, clear_len)) != 0)
        goto cleanup;

#if defined(MBEDTLS_HAVE_TIME)
    {
        /* Check for expiration */
        mbedtls_time_t current_time = mbedtls_time(NULL);

        if (current_time < session->start || (uint32_t)(current_time - session->start) > ctx->ticket_lifetime) {
            ret = MBEDTLS_ERR_SSL_SESSION_TICKET_EXPIRED;
            goto cleanup;
        }
    }
#endif

cleanup:
#if defined(MBEDTLS_THREADING_C)
    if (mbedtls_mutex_unlock(&ctx->mutex) != 0)
        return (MBEDTLS_ERR_THREADING_MUTEX_ERROR);
#endif

    return (ret);
}

/*
 * Free context
 */
void mbedtls_ssl_ticket_free(mbedtls_ssl_ticket_context* ctx)
{
    mbedtls_cipher_free(&ctx->keys[0].ctx);
    mbedtls_cipher_free(&ctx->keys[1].ctx);

#if defined(MBEDTLS_THREADING_C)
    mbedtls_mutex_free(&ctx->mutex);
#endif

    mbedtls_platform_zeroize(ctx, sizeof(mbedtls_ssl_ticket_context));
}

#endif /* MBEDTLS_SSL_TICKET_C */
